Nickel plating



Patented Aug. 25, 1942 NICKEL PLATING Rudolf Lind, Euclid, William J. Harshaw, Shaker Heights, and Kenneth E. Long, South Euclid, Ohio, assignors to The Harshaw Chemical Ohi Company, Elyria, Ohio, a corporation of o No Drawing. Application April 10, 1940,

Serial No. 328,922

. agents have allowed a much heavier deposit of 16 Claims.

This invention relates as indicated to electrodeposition of metals and more specifically, to a process of and materials for use in the process of electrodepositing nickel characterized in that the resultant nickel plate, as deposited, is both bright and ductile. More particularly, the present invention has to do with new addition agents for producing the above-named desirable characteristics in the nickel plate and which may be used with acid nickel baths of usual composition operating under usual conditions.

In order to properly evaluate the present invention, it is necessary to define brightness and ductility or brittleness, terms used in the old art, but used loosely to describe all degrees of brightness or brittleness.

Brightness It is obvious that an extremely thin deposit of nickel over a highly buffed surface will appear bright. Bright plates of this type have been made for years and are well recognized in the art. Their limitations are that if the plated article is exposed to the atmosphere or to wear, the plate soon disappears or wears off. A plate thin enough, so that it will retain substantially the full brightness of the polished base metal is impractical for use even as a base for the electrodeposition thereover of a protective coating of other metals such as chromium. If a heavier deposit is plated out, the brightness of the highly bufled surface diminishes and a gray or white dull deposit is obtained.

A nickel plate which is thick enough to be practical for use and which is bright without bufling is not only desirable per se, but it is particularly advantageous where it is destined for use as the base for an electrolytically deposited chromium plate, since, if the nickel plate does not require to be polished and buffed, a relatively thin plate gives the same protection as the necessarily heavier gray plate, some of which must be taken oil in the polishing to secure the desired brightness. Furthermore, a very considerable saving in time and in cost on the production of plated articles becomes possible, whether with nickel plate per se or with additional chromium finish.

Various so-called addition agents have been proposed from time to time for inclusion in nickel plating baths in order to control or afiect the character of the electrolytically deposited metal. One principal objective in such modification of the plating bath has been to increase the brightness or luster of the deposited metal.

Many of these previous nickel plating addition nickel to be built up before the brightness of the base metal was materially diminished. When polished articles are plated in such baths, the deposit is not truly bright but merely, at best, has the same character as the base metal. The brightness produced by such addition agents may, therefore, be characterized as ,brightness diminishing with increased thickness of plate on a polished surface."

Others of these previous nickel plating addition agents have produced a plate which would maintain the brightness of the polished base surface, even though the plate was built up to a substantial thickness. They would not build up any substantial brightness on an unpolished surface, and at best, would only very slowly build up brightness on an unpolished surface when plates of extreme thickness were made. The bright ness produced by such addition agent may, therefore, be characterized as brightness maintaining itself with increased thickness of plate on a polished surface.

The addition agents of the present invention produce a plate that not only maintains the brightness of the most highly polished base metal, irrespective of the thickness of the plate within practical limits, but also increases in brightness with increase in thickness of the plate on an unpolished surface. The brightness produced by such addition agents may, therefore, be characterized as brightness increasing with thickness of plate on an unpolished surface.

Ductility The question of ductility is one of vital concern to the plater. In general, all bright plates are harder and, therefore, more brittle than ordinary dull nickel. When enough of many of the previously employed addition agents was added to a bath to produce a bright plate, the plate was often too brittle for commercial use and yet if less addition agent was used, the plate would not be fully bright.

A test for ductility may be made by plating on a non-adherent surface and stripping'ofl? the foil and bending it double on itself. A plate .001" thick which will pass this test without breaking is considered to have good ductility. A plate .0005" thick which will just pass this test is considered to have passable ductility. A plate .0002. thick which will not pass this test without breaking is considered to have poor ductility.

The addition agents of the present invention not only produce plates with the highest order of brightness, but also with a high order of ductility as defined by the above scale. This is desirable and essential to the practical use of bright nickel plating.

The principal object of the present invention, therefore, broadly stated, is to provide an improved process of and materials for use in the process of electrodepositing nickel which will not only render the nickel 'plate desirably bright but which will also preserve or render the plate desirably ductile.

Other objects of our invention will appear as the description proceeds.

To th accomplishment of theforegoing and related ends, said invention, then, consists of the means hereinafter more particularly pointed out in the claims, the following description setting forth in detail certain approved modes of operation of our process and combination of ingredients embodying our invention, such disclosure constituting, however, but certain of various forms in which the principles of our invention may be used.

Broadly stated, our invention comprises the discovery that by the use in acid nickel electrolytes of a plurality of addition agents respectively selected from certain different classes of compounds, we are able to produce deposits which are superior to those obtainable by the use of addition agents from either one of such classes alone. We find that the addition agents from one of said classes, although characterized by an embrittling tendency, are productive of extreme brightness when used in combination with addition agents from the other class and that addition agents from said other class not only cooperate in the production of brightness but also exert a ductilizing effect in the combination. The use of one addition agent from each class is preferable but a plurality from each class can be used successfully. Our cooperating addition agents are suitable for use in a wide variety of nickel electroplating solutions. We have found them to be very effective in aqueous acid nickel sulfate solutions and aqueous acid nickel chloride solutions. Among the nickel sulfate solutions in which they are effective are aqueous acid solutions of nickel sulfate, nickel sulfate and nickel chloride, nickel sulfate and sodium chloride, nickel sulfate and hydrochloric acid, nickel sulfate and ammonium chloride, nickel sulfate and alkali metal chlorides other than sodium chloride, the chlorides serving to produce good anode corrosion. Our addition agents are effective in nickel chloride solutions with and without nickel sulfate. In each of said solutions it is desirable, although not necessary,

to employ boric acid or another suitable buffering agent. We prefer to employ a bath containing nickel sulfate together with a suitable chloride, preferably nickel chloride and a suitable buffer, preferably boric acid. We prefer to employ one or more addition agents from one of said classes in quantity to produce the desired brightness and one or more from the other class in quantity to overcome to a substantial extent the resulting embrittling tendency.

As representative of separate classes of compounds which, when used in combination as above stated, produce improved results, are those classes of compounds which may be respectively identified as (1) the amino poly aryl amines in which at least one amino group is connected to an aryl group and (2) aromatic sulfonates, sulfonamides and sulflmides soluble in the path to the extent of at least gram per liter. Since these or both of the aryl groups.

two classes of addition agents are distinct, they will be discussed separately.

Amino poly aryl amines Our invention contemplates, as indicated, the use of amino poly aryl amines. These should have adequate solubility in the plating bath, at least one milligram per liter. The more easily obtainable members of this group of compounds are of the general formula Ar-NH-Ar' and carry one or more amino groups as substituents on one Ar and Ar may be identical or different. Ar and Ar" indicate aromatic cyclic structures such as benzene or naphthalene nuclei which may carry various substituents. Substituents may be such as halogen, hydroxy, sulfonate, nitro and the like groups. Amino and alkyl amino groups are desirable substituents, other groups appear to be slightly undesirable or indifferent although they can be tolerated. Alkyl amino groups or aryl amino groups are suitable as substituents, particularly the short chain alkyl amino groups such as dimethyl amino, methyl ethyl amino groups, etc. Preferably the alkyl chains should not exceed three carbon atoms although longer chains, e. g., up to six carbon atoms can be tolerated. The alkyl amino and aryl amino groups may be considered as species of the broader class of amino groups.

The salts of the compounds of the above described class, for example, the chlorides, hydrochlorides, acetates and sulfates are to be preferred to the compounds themselves because of their greater solubility. It is essential that these compounds, a single one or a mixture of two or more thereof, be present in the solution to an extent to exert their brightening eflect, preferably at least two milligrams per liter.

Some specific examples of compounds suitable for our purpose are as follows:

Table I While the quantity of these substances employed is not sharply critical, they are used in small amounts, that is, amounts of the order of 2 to milligrams per liter, the upper limit being determined by their embrittling effect and. in some cases, by their solubility.

Some of the specific examples of Table I are commercial products, others can be prepared without great difliculty. There are many other amino poly aryl amines which will be found suitable for our purpose. Many of these, however,

are not readily available because they are not commercial products or are difficult to make.

Among the amino poly aryl amines, those having at least one simple amino (NI-I2) group on each aryl group but not more than three amino groups on any aryl group and their salts such as chlorides, hydrochlorides, acetates and sulfates are of outstanding value and constitute a preferred group of brighteners within the scope of the invention.

The second class of materials, representative particular ones of which are employed in combination with one or more substances of the first class of compounds above identified, may be and for the purposes of this specification are designated as aromatic sulfon-compounds. These materials are capable of cooperating with the materials of the first class to produce nickel deposits having a high order of brightness accompanied by commercial ductility.

Particular examples which we have found to give excellent results are as follows:

Table II Alpha-naphthalene mono-sulfonate' Beta-naphthalene mono-sulfonate Naphthalene disulfonates Naphthalene trisulfonates Sulfonated naphthalene o-Benzoic sulfimide (saccharin, preferably as sodium salt) Benzene sulfonamide Benzene sulfohydroxamic acid p-Toluene sulfonamide 0. o-Toluene sulfonamide The above named addition agents of this second class, suitably in the form of the sodium or the nickel salt, may be used in various quantities upwards from 0.2 g./l., however, 5 g./l. or less is usually sufiicient concentration for best results. Larger quantities, within the limits of solubility, do no harm.

Specific Example 5 of Table II above is such as maybe produced by reacting 2 parts of 20% oleum on one part of naphthalene at 160 C. for two hours, neutralizing the resulting mixture with nickel carbonate, filtering and diluting to Where quantities of sulfonated naphthalene are referred to hereinafter, it is to be understood that the quantity specified represents roughly the nickel-naphthalene-mixed-sulfonate content of the mixture. Five cc. of the nickel neutralized reaction mixture is taken as equivalent to one gram of nickel-naphthalene-mixed sulfonates. Other mixtures of compounds of the second class of materials also are-satisfactory.

A conventional aqueous acid nickel bath in which the combined use of the two classes of addition agents will be found to give improved results, as above indicated, consists of:

NiS04.6H20 "grams per liter 120-450 55 NiCIaGI-hO do 75 H3303 grams per liter to saturation 15 Sodium lauryl sulfate grams per liter 01.0 Current density amperes per sq. ft Up to 60 pH 1.5-5.5 Temperature F Room to 1'70 1 Where this.compound is referred to, the material sold under the trade name of Duponol M. E. Dry is to be understood. It is sold as the technical compound. Other equivalent surface tension reducing agents may be used instead of Dunonol. Preparations known as 'lergitol 7 and Tergitol 08, sold by Carbide & Carbon Chemicals Co. and said to be sodium secondary alcohol sulfates, may be used instead of Duponol. The quantities required are of the same order.

2 Some heptallydrate is usually present. Where nickel sulfate is used herein in specific examples, this mixture of hydrates is to be understood.

In the above table giving the composition of a conventional bath, sodium lauryl sulfate is added for the purpose of reducing the surface tension in order to prevent pitting of the plate. The sulfates of normal primary aliphatic alcohols, 75

having from 8 to 18 carbon atoms, are a class of compounds preferred for use for this purpose.

Example I NlSOr 6H2O -grams- 240 NlC12-6Hz0 grams 37.5 HJBOu grams 37.5 Sodium lauryl sulfate grams 0.12 2,4,4-triaminodiphen'ylamine grams 0.01 Sulfonated naphthalene grams 4.0 H20 to make cc 1,000 pH 3.3

Example II NiSO4-6HaO grams 240 NiC12-6H2O grams 37.5 H3B03 grams 37.5 Sodium lauryl sulfate grams 0.12 2,4,4'-triaminodiphenylamine'grams--- 0.02 Sulfonated naphthalene grams 1.0 Saccharin (sodium salt) grams 1.5 H20 to make cc 1,000 pH 3.5

Example III NlSO4-6H2O grams 240 NiCl2-6H2O grams 37.5 HsBOo grams 37.5 Sodium lauryl sulfate grams 0.12 4,4'-diamino diphenylamine grams 0.01 Sulfonated naphthalene grams 4.0 H20 to make cc 1,000 pH 3.5

Example IV NiSO4-6H2O grams 240 NiClz 6H2O grams 37.5 HaBOa grams 37.5 Sodium lauryl sulfate grams 0.12 4,4'-diamino diphenylamine grams 0.02 Sulfonated naphthalene grams 1.0 Saccharin (sodium salt) grams 1.5 H20 to make cc 1,000 pH 3.5 Current density amps./sq. ft- 40 Temperature F.

Example V NiSO4-6HzO grams 240 NiClz-GHzO grams 37.5 HaBOs grams 37.5 Sodium lauryl sulfate grams 0.12 2,4,6,2',4',6'-hexamino diphenylamine grams 0.01 Sulfonated naphthalene grams 4.0 H20 to make cc 1,000 pH 3.3

Example VI NiSO4'6H2O grams 240 N'iClz-fiI-IzO grams 37.5 H3303 grams 37.5 Sodium lauryl sulfate grams 0.12 2,4,6,2',4',6',-hexamino diphenylamine grams 0.017 Saccharin (sodium salt) grams 1.5 H20 to make cc 1,000 pH 3.5

of applications Serial Nos. 200,120 and 200,121,

filed April 5, 1938.

Having thus described our invention, what we claim is:

1. An electroplating solution comprising an aqueous, acid solution of a nickel electrolyte of the class consisting of nickel sulfate and nickel chloride, said solution having the capability of producing bright and ductile deposits of nickel, such capability having been imparted thereto by the inclusion therein of cooperating addition agents, one of said addition agents being a substance selected from the group consisting of amino poly aryl amine compounds and mixtures of such substances in which at least one amino group is connected to an aryl group and being present in the solution in amounts of the order of 2-100 milligrams per liter, and the other of said addition agents being selected from the group consisting of naphthalene sulfonates, the single ring aryl sulfonamides and single ring aryl sulfimides and mixtures thereof soluble in the bath to the extent of at least /2 gram per liter and present in solution in the bath to the extent of at least 0.2 gram per liter, said second type addition agent having no poly aryl amine nucleus.

2. An electroplating bath [comprising an aqueous, acid solution of a nickel electrolyte of the class consisting of nickel sulfate and nickel chloride, said solution having the capability of producing bright and ductile deposits of nickel, such capability having been imparted thereto by the inclusion therein of cooperating addition agents, one of said addition agents being present in the bath in concentration of from 2 to 100 milligrams per liter and being a substance selected from the group consisting of amino poly aryl amine compounds and mixtures of such substances in which at least one amino group is connected to an aryl group and the other of said addition agents being present in concentration of at least one half gram per liter and being selected from the group consisting of naphthalene sulfonates, the single ring aryl sulfonamides and single ring aryl sulfimides, and mixtures thereof, said second type addition agent having no poly aryl amine nucleus.

3. An electroplating bath-as defined in claim 2 further characterized in that said first mentioned addition agent is a poly aryl amine compound; each aryl group of which carries an amino group. V

4. An electroplating bath as defined in claim 1 further characterized in that said first mentioned addition agent comprises a diamino diphenyl amine. I

5. An electroplating bath as defined in claim 1 further characterized in that said first mentioned addition agent comprises a triamino div claim 1, further characterized in that said jsolution contains both nickel sulfate and nicke 8. An electroplating solution as claimed in claim 1, further characterized in that said solution contains both nickel sulfate and nickel.

chloride, said nickel sulfate being present in greater quantity than said nickel chloride.

9. An electroplating solution asclaimed in claim 1, further characterized in that said soluchloride.

tion contains both nickel sulfate and nickel chloride and a bufier comprising boric acid.

10. An electroplating solution consisting essentially of an aqueous acid solution of a substance of the class consisting of nickel sulfate, nickel chloride and mixtures thereof, said solution having the capability of producing bright and ductile deposits of nickel, such capability having been imparted thereto by the inclusion therein of cooperating addition agents, one of said addition agents being a substance selected from the group consisting of amino poly aryl amines, salts thereof and mixtures of such substances and being present to the extent of from 2 to milligrams per liter and the other of said addition agents being selected from the group consisting of naphthalene sulfonates, the single ring aryl sulfonamides and the single ring aryl sulfimides and mixtures thereof and being present to the extent of at least one half gram per liter, said second type addition agent having no poly aryl amine nucleus.

11. An electroplating solution as defined in claim 10 further characterized in that said. solution also contains a buffer comprising boric acid. 12. An electroplating solution as defined in claim 10 further characterized in that said solution also contains an aliphatic alcohol sulfate of from 8 to 18 carbon atoms.

1.3. An electroplating solution comprising an aqueous, acid solution of a nickel electrolyte of the class consisting of nickel sulfate and nickel chloride and mixtures thereof, said solution having the capability of producing bright and ductile electrodeposits of nickel, such capability having been imparted thereto by the inclusion therein of cooperating addition agents, one of said addition agents being a substance selected from the group consisting of amino poly aryl amine compounds and mixtures of such substances in which at least one amino group is connected to an aryl group and being present in solution in quantity to produce a substantial brightening effect and the other of said addition'agents being a substance selected from the group consisting of the naphthalene sulfonates, the single ring aryl sulfonamides and the single ringaryl sulfimides and mixtures thereof soluble in the bath to the extent of at least gram per liter and being present in solution in quantity from 0.2 gram perliter to saturation, said second type addition agent having no poly aryl amine nucleus.

14. The invention as defined in claim 13 wherein said first mentioned addition agent is present in solution in quantity from 2 to 100 milligrams per liter and said second mentioned addition agent is an ortho benzoic sulfimide (saccharine, soluble I saccharine) 15.,An electroplating solution as defined in claim 10 further characterized in that the first mentioned addition agent is a diamino diphenyl amine and the second mentioned addition agent is an ortho benzoic sulfimide (saccharine, soluble saccharine) 16. An electroplating solution as defined in claim 10'further characterized in that the first mentioned addition agent is a triamino diphenyl amine and the second mentioned addition agent is an ortho benzoic s'ulfimide (saccharine, soluble saccharine) RUDOLF LIND. WILLIAM J. HARSHAW. KENNETH E. LONG. 

